In an extraordinary intelligence coup, the double agent left Yemen, traveling by way of the United Arab Emirates, and delivered both the innovative bomb designed for his air attack and critical information on the group's leaders to the C.I.A., Saudi and other foreign intelligence agencies.

After spending weeks at the center of the terrorist network's most dangerous affiliate, Al Qaeda in the Arabian Peninsula, the agent provided critical information that permitted the C.I.A. to direct the drone strike on Sunday that killed Fahd Mohammed Ahmed al-Quso, the group's external operations director and a suspect in the bombing of the American destroyer Cole in Yemen in 2000.

He also handed over the bomb, designed by the group's top explosives expert to be invisible to airport security, to the F.B.I., which is analyzing its properties.

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A senior American official said the high-grade military explosive—which "undoubtedly would have brought down an aircraft"—was sewn into a pair of "custom fit" underwear that even a careful pat-down would find difficult to detect, reports the Times. Unlike the unsuccessful underwear bomb from December 2009, it is reported that these explosive undies could be detonated in two ways, in case one failed. [NYT]